Beta‐TrCP is a component of the ubiquitin ligase complex targeting β‐catenin for proteasomal degradation, and is a negative regulator of Wnt/β‐catenin signaling. To determine whether genetic alterations of the β‐TrCP gene are involved in the development or progression of gastric cancer, we analyzed its somatic mutations in 95 gastric cancers by single‐strand conformational polymorphism and sequencing. We found five missense mutations (5.3%): A99V, H342Y, H425Y, C206Y, and G260E. Tissue carrying mutations showed moderate to strong cytoplasmic and/or nuclear staining of β‐catenin by immunohistochemistry. Thus, somatic mutations of the β‐TrCP gene may contribute to the development of gastric cancer through β‐catenin stabilization.